Group 94/26/05

Jason MaestasTim Ngo

Stephen NeidigkDavid Ortegel

Ch. 38: Computer-Aided ManufacturingCh. 40: Product Design and Process Selection in a Competitive Environment

Ch. 38 Computer-Aided Manufacturing

• 38.1 Introduction• 38.2 Manufacturing Systems • 38.3 Computer-Integrated Manufacturing• 38.4 Computer-Aided Design and Engineering• 38.5 Computer-Aided Manufacturing• 38.6 Computer-Aided Process Planning• 38.7 Computer Simulation of Manufacturing Processes and Systems• 38.8 Group Technology

Introduction

• Computer-aided design (CAD) assists the graphical descriptions of parts.

• Computers are used in the direct control of manufacturing processes and computer-aided manufacturing.

• Computers can also simulate manufacturing processes and systems.

• Group technology approaches allow the rapid recovery of previous design and manufacturing experience and apply information to new situations in a straightforward manner.

Manufacturing Systems

Factors:

Supply and cost of raw materials

National and global market changes

Impact of constantly developing technologies

Machine-tool characteristics and performance

Human behavior and performance

Computer-Integrated Manufacturing

• Computerized integration of all aspects of product design, process planning, production, and distribution, as well as the management and operation of the whole manufacturing organization

• The effectiveness of CIM critically depends on the use of a large-scale integrated communications system involving computers, machines, and their controls.

Figure 39.1 A schematic illustration of a computer-integrated manufacturing system. Source: U. Rembold, et al., Computer-Integrated Manufacturing and Engineering. Addison-Wesley, 1993.

Computer-IntegratedManufacturing

CIM Subsystems• Business planning and support• Product design• Manufacturing process planning • Process automation and control• Production monitoring systems

Functions • Business planning• Business execution

Database

• Product data: Part shape, dimensions, and specifications

• Data management attributes: Revision level, and part number

• Production data: Manufacturing processes used• Operational data: Scheduling, lot sizes, and

assembly requirements• Resources data: Capital, machines, equipment,

tooling, personnel, and their capabilities

Benefits of CIM

• Emphasis on product quality and uniformity, as implemented through better process control

• Efficient use of materials, machinery, and personnel and major reduction of work-in-progress inventory, all of which improve productivity and lower product cost

• Total control of the production, schedules, and management of the entire manufacturing operation

• Responsiveness to shorter product life cycles, changing market demands, and global competition

Computer-Aided Design and Engineering

• CAD involves the use of computers to create design drawings and product models through interactive computer graphics.

• CAE allows several applications to share the information in the database. Applications include (a) finite-element analysis of stresses, strains, deflections, and temperature distribution in structures and load bearing members, (b) the generation, storage, and retrieval of data, and (c) the design of integrated circuits and various electronic devices.

Elements of CAD systems

Figure 39.3 Various types of modeling for CAD

• Geometric modeling

CAD Representations

Figure 39.4 (a) Boundary representation of solids, showing the enclosing surfaces of the solid model and the generated solid model. (b) A solid model represented as compositions of solid primitives. (c) Three representations of the same part by CAD. Source: P. Ranky.

Octree representation

Figure 39.5 The octree representation of a solid object. Any volume can be broken down into octants, which are then identified as solid, void, or partially filled. Shown is two-dimensional version, or quadtree, for representation of shapes in a plane.

38.5 Computer-Aided Manufacturing• Computer-aided manufacturing (CAM):

– The use of computers to assist in all phases of manufacturing.

• CAD/CAM systems: – Features:

• Information can be transferred from the design stage into the stage of planning for manufacture without the need to reenter the data on part geometry manually.

• Database developed during CAD is stored and processed further by CAM into the necessary data and instructions for operating and controlling production machinery, material-handling equipment, and automated testing and inspection for product quality.

• Has the capability to describe the tool path in machine operations to check for possible tool collisions with clamps, fixtures, or other interferences visually.

- Reduces design effort, tryout, and prototype work and significantly reduces manufacturing costs and improves productivity.

• Benefits of CAD/CAM

- Example: the two-engine Boeing 777 passenger airplane.- Designed by computer (paperless design) with 2000 workstations linked to eight computer.- Developed from CAD/CAM software , and no prototypes or mockups were built.- Cost for this development was $6 billion.

– Applications of CAD/CAM systems:• Programming for numerical control and industrial

robots.• Design of dies and molds for casting.• Dies for metalworking operations.• Design of tooling and fixtures and EDM electrodes.• Quality control and inspection.• Process planning and scheduling.• Plant layout.

38.6 Computer-Aided Process Planning (CAPP)

• CAPP is concerned with selecting methods of production: tooling, fixtures, machinery, sequence of operations, and assembly.

• When done manually by process planners, this task is highly labor-intensive and time-consuming and relies heavily on their experience.

• In CAPP individual steps involved in making each part are coordinated with others and are performed efficiently and reliably.

• CAPP is effective particularly in small-volume, high-variety parts production.

• A document containing the sequence of processes and operations to be performed, the machines to be used, the standard time for each operation, and similar information.

• Individual routing sheets are stored in computers affixed with a barcode or other id to the part for future reference.

• Elements of CAPP systems– Variant system (Derivative System)

• Searches are made in the database for existing plans based on its shape and manufacturing characteristics.

• Contains information such as the types of tools and machines to use, sequence of operations to be performed, the speeds, the feeds, and time required for each sequence.

• Minor modifications can be made to existing plans.

– Generative system.• Generative system is capable of creating a new plan instead

of having to use and modify an existing plan.• Contains detailed information of the part shape and

dimensions; process capabilities; selection of manufacturing methods, machinery, and tools; and the sequence of operations.

• It has advantages such as: flexibility and consistency for the process planning for new parts; and higher over planning quality which optimizes the planning and utilizes up-to-date manufacturing technology.

38.7 Computer Simulation of Manufacturing Processes and Systems

• Simulation takes two basic forms:– It is a model of an operation intended to determine the viability of a

process or to optimize its performance.– It models multiple processes and their interactions to help process

planners and plant designers layout machinery and facilities.

• Group Technology (GT)– A concept that seeks

to take advantage of the design and processing similarities among the parts to be produced.

Figure 38.12 Grouping parts according to their geometric similarities and manufacturing attributes.

– Advantages of group technology• Makes possible the standardization of part design and the

minimization of design duplication, which saves time and effort.

• New and less experienced engineer can benefit from previous designs and process plans made by the more experienced.

• Manufacturing costs, statistics on materials, processes, number of parts produced, and other factors can be obtained easily.

• Setup times are reduced, and parts are produced more efficiently and with better and more consistent product quality.

• Improves productivity and reduces cost by 5% to 75%. Which saves lots of $$$.

Chapter 40:

Product Design and Process Selection in a Competitive

Environment

40.1 Introduction

• Today the task of producing high-quality products has become a major challenge.

• There are Extensive varieties in Materials and manufacturing processes.

• Product Design, Product Quality and Life Expectancy, Life-Cycle Assessment and Engineering, Material Selection, Material Substitution, Manufacturing Process Capabilities, Process Selection, Manufacturing Cost

40.1: Product Design

• Advances in Materials and technologies are being made Continually for the manufacturing and Assembly of products.– Software packages such as

Pro-E are readily available – These advance help with the

development for products, by allowing designer to develop Fewer components, and reduce assembly time and manufacturing cost

Design Considerations• Have all alternative product designs been investigated thoroughly?• Can the design be simplified and the number of its components minimized

without adversely affecting its intended functions and performance?• Can unnecessary features of the product or components be eliminated or

combined with other features?• Are some of the components commercially available?• Have modular design and building-block concepts been considered for a

family of similar products and for servicing and repair, upgrading, and installing options?

• Can the design be made smaller and lighter?• Are there specified dimensional tolerances and surface finish unnecessarily

tight?• Will the difficulty or excessively time consuming to assemble and

disassemble for maintenance, servicing, or recycling of its components?• Is the use of fasteners minimized?

Product design and quantity of material

• The cost of materials can significantly be a large portion of a products cost

• Cost of material cannot be reduced below market levels but the quantity of materials can be reduced.

Design Problems

• Thin Cross-sections– Casting or molding of thin cross-section can present

difficulties in die and mold filling and maintaining dimensional accuracy and surface finish

– Forging requires high forces, due to friction and rapid cooling

– Impact extrusion becomes difficult– Formability decreases and thickness decreases– Machining and grinding causes part distortion, poor

dimension accuracy, and chatter– Welding thin sheets causes significant distortion

Design Problems

• Large Cross-sections:– In casting and injection molding, production rate

decreases– Unless controlled, porosity can develop– Bendability decreases as thickness increases– In powder metallurgy, there are significant variations

in density and properties throughout the part– Welding presents problems in depth and quality of

weld joint– In die cast, thicker cross-section will have a lower

strength per unit than this cross section because of the thicker grain sizes

40.3: Product Quality and Life Expectancy

• A well defined technical consideration in development and a human option

• Characteristics:– Satisfies the need and

expectations of the customer, including the cost.

– Compatible with the customers working environment.

– Products functions are resalable and safe over its life

– Aesthetics– Instillation, maintenance, and

future improvements easy to perform at low cost

– Availability in quantities when desired

Return on quality (ROQ):

• Basis components:– Quality must be view as an investment– There needs to be a limit on how much should

be spent on quality improvements– Expenditure specifically should be made

toward quality improvement– Incremental improvement in quality VS.

Additional cost involved must be reviewed

Life Expectancy of Products:

• Life expectancy of products can vary, depending on the materials used and processes employed, and the quality of the product

40.4 Life-Cycle Assessment and Engineering; Sustainable

Manufacturing• Life cycle include:

– Extraction of Natural resources

– Processing of the raw materials

– Manufacturing of products– Transportation and

distribution to the consumer

– Use, maintenance, and reusability of product

– Disposal of the product or recovery and recycling of its components

• Life Cycle Assessment (LCA):– A systematic set of procedures for

compiling and examining the inputs and outputs of material and environmental impacts of producing a product.

• Life Cycle Engineering:– Deals with greater depth with

design, optimization and technical considerations for each component of a product that will effect the environment.

• Sustainable Manufacturing:– There are limited natural resources– The necessity to conserve material and energy– Increase life cycle of products– Eliminate damage to environment– Ensure collective well being for future generations

40.5 Material Selection for Products

• Mechanical and physical properties:– Strength, toughness, ductility, stiffness,

hardness, and resistance to fatigue, creep, and impact, Density, melting point, specific heat, thermal and electrical conductivity, Oxidation and corrosion

– Material selection has become easier and faster because their availability and the extensive databases.

• Considerations:– Do selected material have the appropriate

manufacturing characteristics?– Can some material be replaced by others less

expensive materials?– Do the selected materials have properties that

unnecessarily exceed minimum requirements?– Are the raw material available in standard shapes,

dimensions, tolerances, and surface characteristics?– Is the material supply reliable?– Does the material present any environmentally

damaging effects?

Shapes of Commercially available materials:

• Available forms, such as castings, extrusions, forgings, bars plates, sheets, foil, rods, wires and metal powders

• Preformed materials cut cost on product manufacturing

• Dimensional tolerances, surface quality, and straightness need to be taken accounted for

TABLE 40.1Material Available asAluminumCopper and brassMagnesiumSteels and stainless steelsPrecious metalsZincPlasticsElastomersCeramics (alumina)GlassGraphite

P, F, B, T, W, S, IP, f, B, T, W, s, IP, B, T, w, S, IP, B, T, W, S, IP, F, B, t, W, IP, F, D, W, IP, f, B, T, wP, b, Tp, B, T, sP, B, T, W, sP, B, T, W, s

Note: P, plate or sheet; F, foil; B, bar; T, tubing; W, wire; S,structural shapes; I, ingots for casting. Lowercase letter indicates limited availability. Most of these materials are alsoavailable in powder form.

Reliability of material supply

• A constant flow of material is very important for production

• Geopolitical factor can effect supply

• Strikes, material shortages

Cost of Materials and processing

• Unit cost of raw material depends on the material itself, shape, size, and condition.

• Cost is determined by cost per unit weight or cost per unit volume.• Fluctuations in cost by factors such as supply and demand or

geopolitics

TABLE 6.1 Approximate Cost per Unit Volume for Wrought Metals and Plastics Relative toCost of Carbon SteelGoldSilverMolybdenum alloysNickelTitanium alloysCopper alloysZinc alloysStainless steels

60,000600200–2503520–405–61.5–3.52–9

Magnesium alloysAluminum alloysHigh-strength low-alloy steelsGray cast ironCarbon steelNylons, acetals, and silicon rubber

*

Other plastics and elastomers*

2–42–31.41.211.1–20.2–1

*As molding compounds.Note: Costs vary significantly with quantity of purchase, supply and demand, size and shape, and various other factors.

Chapter 40.6-40.9

•Material Substitution•Manufacturing Process Capabilities•Process Selection•Manufacturing Cost and Cost Reduction

Materials Substitution

• Many reasons for materials substitution– Reduce Costs– Improve manufacturing,

assembly, and installation– Improve performance– Reduce maintenance

Materials Substitution

• An example of Materials Substitution would be in the automotive industry

Manufacturing Process Capabilities

• Each manufacturing process has advantages and limitations– Sand casting not very dimensionally accurate

• Choosing the right method to make the part

Manufacturing Process Capabilities

• Dimensional tolerances and surface finish– The closer the dimensional tolerances and the better

the surface finish the more expensive and time consuming to manufacture

Manufacturing Process Capabilities

• Lead time– Time required to begin production

• Robustness of manufacturing process and machinery– Defined as a process or a system– Choosing the right manufacturing method

taking all variables into account– Variable as large as materials and as minute

as temperature

Process Selection

• Many things must be taken into consideration when selection a process

• Things to think about- geometric features of part production rate, are there tools to make the part

• Goal is to make manufacturing as easy and inexpensive as possible

Figure 40.2 Various methods of making a simple part: (a) casting or powder metallurgy, (b) forging or upsetting, (c) extrusion, (d) machining, (e) joining two pieces.

Manufacturing Costs and Cost Reduction

• For a product to be successful its cost must be competitive with that of similar products

TABLE 40.5Type of machinery Price range

($000)Type of machinery Price range

($000)Broaching 10–300 Machining center 50–1000Drilling 10–100 Mechanical press 20–250Electrical discharge 30–150 Milling 10–250Electromagnetic and electrohydraulic 50–150 Ring rolling 500Fused deposition modeling 60–120Gear shaping 100–200Grinding Robots 20–200 Cylindrical 40–150 Roll forming 5–100 Surface 20–100 Rubber forming 50–500Headers 100–150 Stereolithography 80–200Injection molding 30–150 Stretch forming 400–> 1000Boring Transfer machines 100–> 1000 Jig 50–150 Welding Horizontal boring mill 100–400 Electron beam 200–1000Flexible manufacturing system > 1000 Spot 10–50Lathe 10–100 Ultrasonic 50–200 Single- and multi-spindle automatic 30–250 Vertical turret 100–400Note: Prices vary considerably, depending on size, capacity, options, and level of automation and computer controls.

Manufacturing Costs and Cost Reduction

• Total costs include• Materials costs• Tooling costs-costs

involved in making the tools, dies, molds required to manufacture

•Capital costs- investment in building, land, machinery, and tooling

Manufacturing Costs and Cost Reduction

• Fixed costs- power, fuel, taxes on real-estate

• Indirect labor costs- servicing the total manufacturing operation, supervision, repair, quality control, research and sales

Manufacturing Costs and Cost Reduction

• Typical approximate breakdown of costs in manufacturing today– Design 5%– Material 50%– Direct Labor 15%– Overhead 30%

Bibliography

• http://www.gdrc.org/uem/lca/lca-define.html• www.MetricMetal.com• http://www.aluminum.org/Content/NavigationMenu/The_Industry/-

Wire,_Rod_and_Bar/-Wire,_Rod_and_Bar.htm• http://www.natfhe.org.uk/?id=hestrikepics• http://www.ptc.com